How can I make a cylindrical outline to a mesh (2.9)
One way of doing this would be to start with your base shape (this is an obviously simplified version):

Use insets and/or edge loops to give a &quot;seam&quot; to your edges.

Select the &quot;seam edges&quot;, right-click and select &quot;Extrude Faces Along Normals&quot; and drag the mouse to bring out the edges to your desired depth. You may also want to check &quot;offset even&quot; in the operator panel in the bottom left corner.

Once you have the desired width/depth to your &quot;Seams&quot;, add a Subdivision Surface Modifier to round them out. Don't forget to shade smooth.